professor
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"Now I want you to go in that bag and find my wallet." / KMMFA
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Post by professor on Feb 24, 2020 14:27:24 GMT -5
I have two 70s Fender Champs. I was using a Y cable to go into the two amps for a massive 2x8 sound. My guitar friend noted that wasn't necessary, I could just run a cable out of the other input in to the second amp.
So how does this work, that the signal can also go out? Did Leo Fender design them this way? My bassist friend said that they are also parallel, not in series.
It's good to learn something!
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Post by hushnel on Feb 24, 2020 15:02:52 GMT -5
I didn’t either, but it makes since if both imputes are going into a single amp channel.
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Post by Peegoo 🏁 on Feb 24, 2020 18:48:24 GMT -5
It wasn't a conscious thing Leo & Co. did to allow slaving one amp from another. Players just sort of figured it out. It's because of how the two inputs are wired (parallel). It's a mono amp, so anything plugged into one of the jacks produces the same signal as if it were plugged into the other jack on the same amp. It's sort of like a Y cable built into the front of the amp. The only caveat is on amps with HI and LO input jacks. The LO jack usually has a resistor to pad the signal down a little to prevent hotter pickups from overdriving the preamp. You can jumper multi-channel amps to *themselves* if they have two input jacks per channel. Marshall guys have for years been adding a little jumper across the inputs of their four-jack/two-channel amps to get a bigger sound:  |
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pdf64
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Post by pdf64 on Feb 24, 2020 19:00:35 GMT -5
To make it as an output, the signal has to pass through an additional 136k (typically) of series resistance. When combined with the inherent capacitance of the link cable, that may roll off some high end frequencies, as well as increase the susceptibility to pick up hum.
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swampyankee
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Fakin' it 'til I'm makin' it since 1956
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Post by swampyankee on Feb 28, 2020 14:40:13 GMT -5
I used to do jumper the channels with my Tweed Deluxe clone, and I've heard it done with blackface and silverface amps as well, although I've never tried it.
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Post by areaman on Apr 13, 2020 10:45:48 GMT -5
You can't really do the "jumper the channels" thing with Blackface or Silverface amps.I'm referring specifically to Fender two-channel amps with Normal and Vibrato channels, typically four total inputs.
The Normal and Vibrato channels are out-of-phase. When you jumper inputs from the Normal to the Vibrato channel (or vice versa), there will be dead spots as you twiddle with the two channel volume controls. These dead spots are where the out-of-phase signals cancel each other out.
This doesn't occur with tweed amps and tweed-circuit copies like Marshalls. You won't break anything, and if the partially canceled signal gets you something tone-wise you like, go for it.
This is not the same thing as plugging your guitar into one amp's input #1, and inserting a cable into input #2 and running that to a second amp. Two separate amps, no out-of-phase issues.
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pdf64
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Post by pdf64 on Apr 13, 2020 12:23:54 GMT -5
You can't really do the "jumper the channels" thing with Blackface or Silverface amps.I'm referring specifically to Fender two-channel amps with Normal and Vibrato channels, typically four total inputs.
The Normal and Vibrato channels are out-of-phase... You may be forgetting about the non reverb models. It’s the reverb - dry mixer stage at V4 6-8 section that flips the polarity of the ‘vibrato’ channel. The channels of non reverb models are in the same polarity, so mixing them together is a thing. For some weird trem effects, try mixing those channels on the reverb models though, with the trem running. That seems akin to saying that the speakers on a stereo can’t be connected in opposing polarity? I agree that it may not be immediately obvious that 2 rigs being used simultaneously may be in opposing polarity; however the use of a polarity flip switch on one of them will make it apparent. Opposing polarity signals may tend to make it seem like the soundstage is extremely wide but with an ill defined, hollow centre. In the bad old days of ‘90s I used to play out with a monster stereo rig. |
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Post by areaman on Apr 14, 2020 19:02:16 GMT -5
My understanding is the "polarity flip switch" on the rear panel changes polarity of the A/C current, not speaker phase and not electronic circuit channel phase.
Individual speakers have "polarity". Multiple speakers connected to one another *in the same amp* have "phase". I suppose two separate single-speaker amps run in stereo could possibly have their individual speakers out-of-phase, but I've never looked. Got a battery?
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Post by rdr on Apr 15, 2020 9:59:10 GMT -5
You can't really do the "jumper the channels" thing with Blackface or Silverface amps.I'm referring specifically to Fender two-channel amps with Normal and Vibrato channels, typically four total inputs.
The Normal and Vibrato channels are out-of-phase. When you jumper inputs from the Normal to the Vibrato channel (or vice versa), there will be dead spots as you twiddle with the two channel volume controls. These dead spots are where the out-of-phase signals cancel each other out.
This doesn't occur with tweed amps and tweed-circuit copies like Marshalls. You won't break anything, and if the partially canceled signal gets you something tone-wise you like, go for it.
This is not the same thing as plugging your guitar into one amp's input #1, and inserting a cable into input #2 and running that to a second amp. Two separate amps, no out-of-phase issues.
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Post by rdr on Apr 15, 2020 10:01:40 GMT -5
I use a Radial Bigshot aby switch to jumper the channels of a reverb Fender amp, with one output of the pedal set to 180 out of phase. Works great. With my non-reverb Bandmaster, this is not necessary.
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pdf64
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Post by pdf64 on Apr 15, 2020 15:02:38 GMT -5
My understanding is the "polarity flip switch" on the rear panel changes polarity of the A/C current, not speaker phase and not electronic circuit channel phase. Individual speakers have "polarity". Multiple speakers connected to one another *in the same amp* have "phase". I suppose two separate single-speaker amps run in stereo could possibly have their individual speakers out-of-phase, but I've never looked. Got a battery? I think the context of this thread is audio signals, rather than mains / wall outlet. The terminology and understanding of signal phase and polarity is very widely misused and misunderstood. To help get your head around things, try having a read through thehub.musiciansfriend.com/tech-tips/polarity-versus-phase |
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Post by thumbpicker on Feb 3, 2021 18:58:46 GMT -5
wouldn't the phase reversal not be an issue if you wired the jumper cable you use to tip to sleeve and into the next amp or channel?
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pdf64
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Post by pdf64 on Feb 3, 2021 19:46:11 GMT -5
wouldn't the phase reversal not be an issue if you wired the jumper cable you use to tip to sleeve and into the next amp or channel? If both amps were safely grounded, that would short the signal out, to the second amp at least. If ungrounded, the second amp would have a massive buzz interference, due to using screen (and the first amp’s chassis!) wired to its tip / hot. |
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